Support brackets for chair armrests or backrests are known, consisting of an upper part or pad on which the arm or back of the chair user rests, a vertical support and a horizontal blade for its fixing to the chair frame.
These brackets however present the drawback of lack of flexibility and modularity.
In this respect, seeing the large variety of chairs and applications, it is important that these armrest and backrest brackets can be modified in terms of their main dimensions.
The known art often uses plastic or aluminium parts obtained by injection moulding, which by their very nature are very rigid in adapting to the individual person.
To obviate these drawbacks, brackets have been proposed consisting of separate vertical support elements and horizontal fixing elements welded together.
This arrangement only partly solves the problems as the parts produced in this manner are in any event bulky and rigid when the parts are combined. They also present considerable aesthetic problems which can be solved only by applying coverings on the weld region and by costly cleaning operations.
Another proposed arrangement consists of a single bent blade which performs both the bracket and support function. This arrangement however presents evident limits in terms of bulk, appearance and modularity.
Another proposed arrangement is to fix the blade to a tubular support element by screwing it onto a bush welded inside the tubular element.
This arrangement has the drawback of substantial cost due to welding and to the use of a relatively costly element such as the lathe-turned bush.
Moreover it does not enable the blade to be reliably orientated relative to the support, so that semi-permanent screwing operations have to be carried out in the factory (with the same drawbacks as the other arrangements) or further manufacturing costs have to be incurred by using insertion fitting between the parts.
Brackets are also known which enable the height of the arm/back support to be adjusted by the use of telescopic elements.
These known brackets present however certain drawbacks and in particular:                slackness and jamming while sliding,        complicated construction,        a large number of components leading to high cost and possible reliability problems,        non-ergonomic adjustments.        
With regard to the problem of sliding the telescopic elements within height-adjustable brackets, the known art has already proposed different solutions.
The most frequent solution, in which the sleeve is rigid with the arm/back support and slides directly on the surface of the vertical support element (tubular or blade) presents the drawback of unacceptable slackness as it is difficult to achieve a constructional precision which eliminates gaps within the guide regions.
Another drawback consists of the fact that the sliding between the constituent rigid material of the sleeve (typically polyamide filled with glass fibre) and the outer surface of the tubular element determines continuous rubbing leading to surface deterioration.
To solve this problem brackets have been proposed in which the tube slides internally via an additional guide while the outer sleeve has only an aesthetic function. Again in this case the addition of another important element leads to additional costs and does not fully solve the problem of sliding precision because of the aforesaid known problems.
In other cases use is made of bands of self-lubricating material rigid with one of the telescopic elements, which improve sliding without ruining the outer surface. However to apply these bands and maintain them in position, costly arrangements have to be used comprising seats obtained by rectifying machining or fixtures with movements to obtain undercuts, or open half-shells which once assembled enclose one of the telescopic elements.
The known art presents various solutions for locking the movement of the telescopic elements of the brackets.
In some cases controls are provided connected to a transmission which by means of a cam disengages a catch from the holes provided in the other telescopic element.
These solutions present the drawback of being complicated in terms of the large number of parts and of the difficulty and time of assembly.
Other simpler solutions exist comprising a control, usually a pushbutton, connected directly to the catch. However this penalizes the ergonomics of the bracket as the position of the control and the type of control movement are uncomfortable, not immediate and unnatural.